The present invention relates to a ferromagnetic material which consists chiefly of an iron-silicon system alloy and which has good corrosion resistance and high saturation flux density. More particularly, the invention relates to a ferromagnetic material which consists of a multilayered film having good corrosion resistance, high saturation flux density and high permeability, and to a magnetic head employing the above ferromagnetic material which is suited for high density magnetic recording.
So far, ferrites such as Mn-Zn ferrite and ferromagnetic alloys such as permalloy, sendust, and the like, have been placed in practical use as materials for producing magnetic head cores. These materials, however, have saturation flux densities of as small as about 10 kG, and are not suited for realizing high density magnetic recording.
In recent years, therefore, study has been forwarded with regard to an Fe--Ti crystalline alloy having a saturation flux density of 15 kG and a Co--Zr amorphous alloy having a saturation flux density of 14 kG, which, however, have not yet been put into practical use.
The Fe--Si system alloy has generally been known as a material which has a high saturation flux density, and is much used for forming the cores of transformers. However, the Fe--Si system alloy has poor corrosion resistance and is easily oxidized in the air. The cores of transformers are submerged in an oil and are not exposed to the air. However, the Fe--Si system alloy could not be used at the ends of the head cores that are exposed to the air at all times.
A single layered film having a thickness of about 1 .mu.m obtained by sputtering the Fe--Si system alloy has a permeability of 300 to 500 and a coercive force of several oersteds. This single layered film, however, is not still satisfactory as a material for making magnetic heads. It is therefore urged to provide a material having a larger permeability and a smaller coercive force.
As described above, there is available no ferromagnetic material which has good corrosion resistance, high saturation flux density, and sufficiently high permeability, and which is suited for producing magnetic head cores. Therefore, it has been desired to develop a magnetic head for high density recording having excellent recording/reproducing characteristics, by using a core material which has characteristics suited for a head material for high density recording.
The following references are cited to show the state of the art; (i) Japanese Utility Model Laid-Open No. 58613/1977, (ii) Japanese Patent Laid-Open No. 54408/1977, (iii) Japanese Patent Laid-Open No. 112439/1981.